Frost on Walls

DEAR TIM: I have frost forming on some of my exterior walls. This has never happened before, and it's freaking me out. What's causing this to happen? Can it damage my home? Dana S., Bena, MN

DEAR DANA: When the temperature drops well below zero, which happens with regularity in Minnesota during the winter, you bet you can get frost on cold interior surfaces.

Inside your home the air is warm. This warm air can hold a fair amount of water vapor. When warm, moist air contacts a cold surface, it can condense. You've probably seen this in the summer if you take a cold can of soda or pop onto your patio to relax. Within minutes water droplets start to form on the outside of the can.

This same thing is happening on the walls of your home. But the walls are so cold, the water that is condensing is turning to ice and frost.

It can cause damage once it thaws and runs down the wall. What's more, there is a possibility the water vapor is collecting inside the wall. This is a far more serious problem if it's happening.

You can minimize the frost from forming by trying to lower the humidity inside your home. This is not always easy, but check to make sure your humidity setting on your humidifier is set very low. As the outdoor temperature drops, you need to make sure you put less water in the air in your home.

Water vapor also is generated by cooking, showers, hanging things to dry, indoor plants and even aquariums. Just try to watch the water you use indoors in cold weather.

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